Around the World: Atlantic Warming Melts Antarctic Ice

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Though physically about as distant from Antarctica as you can
get, water masses in the North and Tropical Atlantic Ocean
significantly influence the effects of climate change on the icy
southernmost continent, new research suggests.

Antarctic climate has changed considerably over the past several
decades, with the Antarctic Peninsula — located on the West
Antarctic Ice Sheet — experiencing more warming than any other
region on Earth. Researchers have long recognized that
atmospheric and oceanographic conditions,
such as wind speed and direction, in the southern Pacific
Ocean play an important role in the climate of Antarctica and the
distribution of its ice. But Pacific conditions cannot entirely
explain all the changes currently occurring in and around
Antarctica, particularly during the austral (Southern Hemisphere)
winter. [ North
vs. South Poles: 10 Wild Differences ]

Now, a team of researchers based at New York University has
studied more than 30 years of atmospheric data collected from
around the world to try to identify other key atmospheric players
in Antarctic climate. The team found that water temperatures in
the North and Tropical Atlantic Ocean correlate strongly with
sea-level pressure in
Antarctica's Amundsen Sea, which influences the behavior of
sea ice in the region.

"Those things stuck out as a sore thumb that said they were
related," study co-author David Holland told LiveScience. "That
doesn't mean one thing causes the other, but they are strongly
related."

The team next tested whether the correlation between Atlantic and
Antarctic water masses represented a true cause-effect
relationship, or whether it was just a coincidence. To do so, the
researchers used atmospheric
models to simulate changes in the Antarctic climate under
various global atmospheric and oceanic conditions. To their
surprise, they found that directly raising temperatures in the
North and Tropical Atlantic in their models did, indeed, have the
same effects on wind patterns and ultimately the distribution of
sea ice around Antarctica as the historical records showed
happened in real life.

This suggests that the Atlantic temperatures and Antarctic sea
ice are causally linked, Holland said.

It may seem counterintuitive that ocean temperatures in one
hemisphere could have such a large impact on ice distribution in
another hemisphere. However, as Holland explained, Atlantic
conditions propagate out of the Northern Hemisphere in an
atmospheric ripple effect: Warm water masses in the Atlantic
change atmospheric conditions that eventually turn the gears of
the Southern Hemisphere's atmospheric patterns, finally getting
sucked down into the region surrounding Antarctica.

Next, the team hopes to better understand what drives the yearly
and decadal changes in the North and Tropical Atlantic Ocean that
have caused observed changes in Antarctica over the past 30
years. They also want to better understand why ice in Antarctica
reacts to climate change
differently than does ice in the Arctic. Antarctic ice has been
redistributed more than it has disappeared in recent years, while
Artic ice has experienced more melting.